Modified coins have no collector value, any value would be associated with the ring.
Without seeing the mark inside you would need to take it to a jeweler to find out if it is 18 Karat gold and the RGP is the makers mark or if it is Rolled Gold. A qualified jeweler can identify the item for you and will advise you on what it is and its value.
18k rgp is "rolled gold plate"
RGP stands for rolled gold plated. An 18 RGP mark on jewelry means the jewelry is not a real 18k gold but only gold plated.
rolled gold plated
£456 p
1 dollar
It will depend on the weight.
4 million dollars
Just a lost boy who needs to close his eyes and find what i have given over and over agian his twin. I love
Jewelry engraved with RGP, which stands for Rolled Gold Plating, or plaqué d'or laminé, (proper designation: 1/30 14 kt.), contains approximately 100 times the average amount of gold utilized in gold plating (which is either sprayed or dipped). Rolled Gold Plating involves the lamination of a thin sheet of gold leaf with a lesser metal (usually brass), fused by heating under pressure.
What does 18kHGA mean stamped in a ring
Google search for "18 gauge tongue ring"!